Preparation of 4-pregnen-17alpha-ol-3, 20-dione



United. States Patent PREPARATION OF 4-PREGNEN-l7oc-OL-3,20-DIONE JohnM. 'Chemerda, Metuchen, Earl M. Chamberlin, Westfield, and Edward W.Tristram, Cranford, N. J., assignors to Merck & Co., Inc., Rahway, N.J., a corporation of New Jersey No Drawing. Application November 4,1955, Serial No. 545,132, now Patent No. 2,833,790, dated May 6, 1958,which is a division of application Serial No. 472,756, December 2, 1954,now Patent No. 2,777,843, dated January 15, 1957. Divided and thisapplication January 7, 1957, Serial No. 632,674

2 Claims. (Cl. 260397.4)

This invention relates to the preparation of 4-pregnen-17a-ol-3,20-dione and particularly to the preparation of4-pregnen-17a-ol-3,20-dione from S-halo-bisnorcholanal, and tointermediates thus obtained.

This application is a division of our copending application Serial No.545,132, filed November 4, 1955, and now Patent No. 2,833,790, which isa division of our copending application Serial No. 472,756, filedDecember 2, 1954, and now Patent No. 2,777,843.

7 The discovery of the remarkable properties of cortisone andhydrocortisone and similar related compounds, has stimulated wideinterest in finding simpler and more economical methods of preparingsuch compounds. One of the more recent methods which has been developedfor preparing these valuable steroids is the introduction of oxygengroups by subjecting desoxy steroids to the action of microorganisms.This development has led to the increasing importance of desoxy steroidswhich possess all the necessary groups with the exception of oxygengroups which may be introduced by fermentation methods. One of the morevaluable of these desoxy steroids is 4-pregnen- 17a-ol-3,20-dione whichonly lacks the ll-keto and 21- hydroxy groups of cortisone, and the 11pand 21-hydroxy groups of hydrocortisone. These oxygen groups can beadded by fermenting the steroid with various microorganisms, as forexample, fermentation with various strains of Curvularia will introducean llfi-hydroxy group, and fermentation with various strains ofSphaeroidaceae will introduce a 21-hydroxy group.

The preparation of 4-pregnen-17a-ol-3,20-dione has heretofore beencarried out by a costly and complex process which involved theenolization of bisnorcholanal followed by ozonization of the resultingenol ester, reductive decomposition of the ozonide to the corresponding21-keto-pregnane, enolization of this compound to form a 23 -20acetoxy-pregnane, peracid oxidation of the 17,20 double bond to producethe 17,20 epoxide derivative of the unsaturated ester, and finallyhydrolysis of this compound to produce 4-pregnen-17u-ol3,20-dione.

It has been suggested to prepare 5a-halo-bisnorcholanic acids andaldehydes starting with stigmasterol. The halogen in theSoc-halo-bisnorcholanaldehydes represents a potential double bond andyet is impervious to attack during the oxidation of the 3-hydroxyl groupto the 3-keto group.

An object of the invention is to provide a simplified procedure forproducing 4-pregnen-l7a-ol-3,20-dione from readily available startingmaterial. Another object of the invention is to provide a process forthe degradation of the aldehyde group in 5a-halo-bisnorcholanaldehyde tothe 17a-hydroxy-20-keto side-chain without removal of the 5a-hlo group.A further object is to provide valuable intermediates useful in thisprocess. Other objects and the advantages of the invention will appearhereinafter.

In accordance with the invention, 4-pregnen-17a-ol- 3,20-dione (CompoundVII) is prepared by the following series of reactions: brominating aS-halo-bisnorcholanal compound (Compound I) to produce the corresponding5-halo-20-bromo-bisnorcholanal compound (Compound II),dehydrobrominating to produce the corresponding5-halo-17(20)-bisnorcholenal compound (Compound III), treating withperacid to produce the corresponding epoxy formate (Compound IV),hydrolyzing to'yield 5- halo-pregnane-3,17u-diol-20-one (Compound V),oxidation of the B-hydroxy group to form a keto group (Compound VI) anddehydrohalogenating to produce 4-pregnen-17a-ol-3,20-dione (CompoundVII).

As alternate steps to this procedure, the S-halo-bisnorcholanal compound(Compound I) is converted directly to the corresponding5-halo-17-(20)-bisnorcholenal (Compound III) by reacting with bromine inthe presence of a weak base and acatalyst. The epoxy formate (CompoundIV) is converted to 5-pregnene-3,17a-diol-20-one by saponification.

These reactions may be chemically represented wherein R is a groupconvertible to a hydroxy group by hydrolysis and X is a halogen asfollows:

' on, V on, m-c Br- I 0110 R t B l \/l x w x Compound I Compound II x ICH; C") I %\=OC-H $H| l 0 I (J-CHO I R R Compound IV Oompound III on,5:11, l=0 C=O I :---0-rr jou H0 v 0 i Compound V Compound VI CH] 6:0 on

Compound VII The S-halo-bisnorcholanal compound is brominated to producethe corresponding 5-halo-20-bromo-bisnorcholanal. TheS-halo-bisnorcholanal compound has either a 5a-Chl010 or 5a-bromo groupand a substituent at the 3-position which may be readily hydrolyzed to ahydroxy group, such as an ether group of the formula R wherein R is ahydrocarbon group and especially a hydrocarbon radical containing up toand including eight carbon atoms, e. g. methyl, ethyl, propyl,isopropyl, butyl, hexyl, cyclohexyl, benzyl and the like, or an estergroup of the formula OCOR", wherein R is a hydrocarbon radical,especially hydrocarbon radicals containing up to and including sevencarbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, hexyl,heptyl, phenyl, cyclohexyl, and the like.

The bromination may be conveniently carried out by dissolving orsuspending the 5-halo-bisnorcholanal in an organic solvent andsubjecting the solution or suspension to the action of approximately anequal molar amount of bromine. There is suflicient hydrogen bromideformed during the reaction to act as a catalyst. It is preferred to usechloroform as a solvent, although other solvents maybe used, such asacetic acid, formamide and mixtures of solvents, such as aceticacid-pyridine and acetic acidformamide. The reaction temperature governsthe rate of bromination, thus the rate of bromination increases atelevated temperatures. It is ordinarily desired, for convenience, toeffect the bromination at about 20 to 60 C. although temperatures as lowas 0 C. can be used under normal atmospheric pressure. Within thepreferred temperature range the reaction usually is complete in fromone-half to six hours.

The 5-halo-20-bromo-bisnorcholanal compound is readily dehydrobrominatedto produce the corresponding 5-halo-l7(20)-bisnorcholenal. Thedehydrobromination can be readily carried out by heating with metallichalides particularly with lithium chloride in an amide solvent, such asan N,N-dialkylacylamide having the formula wherein R and R are alkylgroups containing from one to six carbon atoms and R' is hydrogen or analkyl group containing from one to six carbon atoms, as for example,N,N-dimethyl formamide, N,N-dimethylacetamide, N,N- diethylformamide,N,N-diethylacetamide, N-methyl-N- ethylformamide,N,N-dimethylpropionamide and N- methyl-N-ethylacetamide. Other metallichalides which may be used are magnesium chloride, beryllium chloride,and aluminum chloride. Hydrogen bromide has also been found to beeffective in place of the metallic halide. The dehydrobromination mayalso be carried out by the use of collidine, pyridine, lutidine,diethylaniline, or other organic bases which are refluxed with thebromo-steroid for a period of time of the order of minutes. The productcan be recovered by filtering, washing with water, and drying.

The S-halo-bisnorcholanal compound is converted directly to thecorresponding 5-halo-l7(20-bisnorcholenal compound. This may be readilycarried out by reacting 4 the bisnorcholanal with bromine in thepresence of a weak base. The weak base is preferably anN,N-dialkylacylamide having the formula N' R/II wherein R, R" and R areas defined above. Typical examples of such amides are:N,N-dimethylformamide, N,N dimethylacetamide, N,N dimethylpropionamide,N,N-diethylformamide, N,N-diethylacetamide, N-methyl- N-ethylformamide,and N-methyl-N-ethylacetamide. The reaction time is reduced by theddition of any of the ordinarily used bromination catalysts such ashydrogen bromide, sulfuric acid or organic sulfonic acids as for examplep-toluene sulfonic acid. The reaction is conveniently carried out atroom temperature which requires from 12 to 28 hours for completion. Theproduct can be recovered by diluting the reaction mixture with water,filtering, and then washing the product with water and drying.

The 5-halo-17(20)-bisnorcholenal compound is treated with an Organicperacid to produce the corresponding epoxy formate(Sat-halo-17,20-epoxy-pregnan-20-ol-3-R- ZO-formate). The organicperacid is preferably an aromatic percarboxylic acid, such as perbenzoicand perphthalic acids, and saturated aliphatic peracids, such asperacetic and persuocinic acids. This reaction results in nearlyquantitative yield of product. The reaction is preferably carried out inan organic solvent, such as ben- Zene, chloroform, or ethyl acetate. Thereaction is preferably carried at from minue 10 to 50 C., although thetemperature may be varied within wide limits. At the preferredtemperature range the reaction requires from 12 to 48 hours forcompletion. The rate of reaction will vary with the temperature. Theproduct can be isolated from the reaction mixture by filtering to removevarious insoluble byproducts and reactants, and then Washing with watercontaining sodium carbonate. The organic layer is dried over sodiumcarbonate and evaporated to dryness under vacuum. The product can alsobe recovered by ether extraction followed by washing with dilute alkaliand water, and evaporating to dryness.

The Soc-halo 17,20 epoxy-pregnan-20-ol-3-R-20-formate is hydrolyzed toyield 5-halo-pregnane-3,17a-dio1- 20-one. The hydrolysis is readilyachieved by treating with an acid in a suitable solvent, such asmethanol, ethanol, acetone, or tetrahydrofuran. Strong acid such ashydrochloric acid, sulfuric acid, perchloric acid, andpara-toluene-sulfonic acid, used in dilute concentrations are preferredfor effecting the hydrolysis. Temperatures ranging from about 0 to C.are usually employed to accomplish the hydrolysis. At room temperature,several minutes to three hours are ordinarily adequate to complete thereaction. The heavy precipitate of product is filtered from the reactionmixture and washed with an organic solvent and dried under vacuum.

The epoxy formate is also converted to S-pregnene- 3,170c-diOl-20-0116by reacting with a basic substance. Water must be present unlessreaction is run in alcohol.

The reactants are preferably brought together in a solvent. Suitablesolvents are methanol, ethanol, hexane, benzene, toluene, xylene,petroleum ether, ether, dioxane, tetrahydrofuran and the like. The basicsubstance may be any of the conventional bases, such as an alkali metalor alkali metal hydroxide, carbonate, bicarbonate or the like, but it ispreferred to use a hydroxide as, for example, sodium hydroxide,potassium methoxide, or potassium hydroxide. The reaction may be carriedout at from 0 to 70 C. At room temperature the reaction requires from 30to minutes for completion. On completion of the reaction the reactionmixture is neutralized by addition of an acid, as for example, glacialacetic acid, and then the solution is partially concentrated byevaporation under vacuum. The

, '5 product is precipitated from the reaction mixture by addition ofwater and is then filtered and washed with water.

The 5-halo-pregnane-3,l7a-diol-20'one is oxidized to produce5-halo-pregnan-17a-ol-3,20-dione. The oxidation is preferably carriedout with a chromic anhydridepyridine complex, although other selectiveoxidizing agents may be used, such as chromic acid. The oxidation may becarried out at a wide range of temperatures, although preferably below50 C. Within the preferred temperature range, with the preferredoxidation agent, the reaction requires from 6 to 24 hours. The productcan be separated from the reaction mixture by conventional means.

The 5-halo-pregnan-17a-ol-3,-20-dione is treated with a basic substanceto form 4-pregnen-17q-ol-3,20-dione. This reaction is .generally carriedoutunder anhydrous conditions. The reactants are preferably broughttogether in a solvent. Suitable solvents are methanol, ethanol, hexane,benzene, toluene, xylene, petroleum ether, ether,dioxaneftetrahydrofuran and the like, The basic substance may be any. ofthe conventional bases, such as an alkali or alkaline earth metalhydroxide, carbonate, bicarbonate or the like but it is preferred to usea hydroxide as, for example, sodium hydroxide or, potassium hydroxide.The reaction may be carried out at from to 70 C. At room temperature thereaction requires from 30 to 120 minutes for completion. On completionof the reaction the reaction mixture, is neutralized by addition of anacid as, for example, glacial acetic acid, and then the solution ispartially concentrated by evaporation under vacuum. The product isprecipitated from the reaction mixture by addition of water and is thenfiltered and washed with water.

The following examples are given for purposes of illustration:

EXAMPLE 1 3 fi-ace foxy-5 a-ch l0r0-2 O-bromobisnorcholanal A solutionof 14.5 grams (0.0354 mole) of 3B-acetoxy- 5a-chlorobisnorcholanal in200 ml. of chloroform was treated with ten grams (0.1 mole) of anhydrouscalcium carbonate and stirred at 2 8 C. To this slurry 46 milli litersof chloroform solution containing 5.5 grams (0.0344 mole) of bromine wasadded dropwise over a period of one-half hour and the reaction mixturestirred for two hours. After filtering to remove calcium carbonate, thechloroform solution was washed with dilute sodium iodide, sodiumthiosulfate solution and then with dilute sodium bicarbonate solutionand finally dried over anhydrous sodium carbonate. The chloroform layerwas then evaporated almost to dryness under vacuum and 100 millilitersof 95% ethanol was added. Upon further concentration the main portion ofproduct precipitated. After standing overnight in the refrigerator theproduct, 3fi-acetoxy-5u-chloro-20-bromobisnorch01analdehyde, wasfiltered, washed with 50 milliliters of 95% ethanol and dried undervacuum; yield 10.6 grams, melting point 175179 C., M1 +'13.-4(chloroform).

Analysis.--Calcd. for C H O ClBr: C, 59.07; H, 7.44. vFound: C, 58.79;H, 7.43.

.-chloro-20-bromobisnorcholanal in 1320 milliliters of dimethylformamidecontaining 5.5 grams (0.068 mole) of hydrogen bromide was allowed tostand at 28 C. for "four days. .an ice bath while 600 milliliters ofwater was added.

The solution was then stirred and cooled in After stirring for threehours the product was filtered,

'washed with water and dried under vacuum to yield 268 grams ofessentially pure 3fl-acetoxy-5a-chloro- 17(20)-bisnorcholenal, meltingpoint 194-19S C., 7\

:maximum 2540, E% 376. Recrystallization from meth- EXAMPLE 3 .iflacetoxyJu-chlorod 7 (20) -bi.morcholenal Two grams (5 millimoles). of3,8-acetoxy-5a-chloro bisnorcholanaldehyde and 0.04- gram of p-toluenesulfonic acid were dissolved in 80 milliliters of dirnethylformamide andstirred at'2'8 C. while 0.8 gram (5 millimoles) of bromine in7milliliters of dimethylformamide was added dropwise over the course ofthree hours. After standing at normal room temperature for 24 hours thereaction mixture was cooled in an ice bath and diluted with 80milliliters of water. The resulting slurry was stirred for an hour andthen filtered. The product was washed well with water and dried undervacuum to yield 1.86 grams of impure 3fl-acetoxy-5a-chloro-17(20)-bisnorcholenal, melting point -158--163 C., maximum 2540 A., E% 200.Several vrecrystallizations from ethanol ,gaveproduct melting at191--193 C., A maximum 2560 A., E% 379. This product showed nodepression in melting point when admixed with unsaturated aldehydeprepared from 3,6-acetoxy-Swchloro-ZO-brommbisnorcholanal.

EXAMPLE 4 3fi-acetoXy-5a-chlore-17,20-epoxypregnan-20-ol formate Asolution containing 15.7 grams (0.9386 mole) of 3/3-acet0xy-5a-chloro-17(20)-bisnorcholenaldehyde in 150 milliliters of dry benzene at10 C. was treated with 56 grams (0.309 mole) of perphthalic acid in 435milliliters of ethyl acetate. The reaction mixture, after standing twodays at normal room temperature, was filtered to remove insolublephthalic acid and washed four times with 500 milliliters of 10% sodiumcarbonate solution. The organic layer was dried over sodium carbonateand evaporated to dryness under vacuum to yield 15.1 grams; meltingpoint 139-142 C.; [a] 5.2 (chloroform). The infrared spectrum of thecrude reaction product was compatible with the epoxy formate formulationand elemental analysis agreed with calculated values.

Analysis.-Calcd. for C H O Cl: C, 65.66; H, 8.04; C], 8.08. Found: C,65.64; H, 7.97; Cl, 8.12.

EXAMPLE 5 5 -pregnene-3 3,1 7a-di0l-20-one One gram (2.4 millimoles) of3fl-acetoxy-5a-chloro- 17,20-epoxypregnan-20-ol formate was dissolved in150 milliliters of ethanol at 30 C. and treated with 30 milliliters of2.5 M sodium hydroxide solution. After standing for ninety minutes atnormal room temperature 6 milliliters of glacial acetic acid was addedand the solution was partially evaporated under vacuum. The product wasprecipitated by dilution with 75 milliliters of water and refrigeratedovernight. The reaction mixture was filtered; the solid was washed withwater and dried under vacuum to yield 0.55 gram of product,5-preguene-3B,17a-diol-20-one, melting at 200-215 C. Recrystallizationfrom ethanol gave a melting point of 205 -2l0 C. which was not depressedupon mixture with authentic 5-pregnene-3B-17e-diol-20-one.

Analysis.Calcd. for C H O C, 75.85; H, 9.70. Found: C, 75.41; H, 9.66.

EXAMPLE 6 5 u-chlor0pregnane-3BJ 7u-diol-20-0ne A slurry of 2.5 grams(5.7 millimoles) of 3fi-acetoxy- 5e-chloro-17,20-epoxypregnane-20-olformate in ml. of methanol was treated at normal room temperature with12.5 milliliters of concentrated hydrochloric acid. A greenish-bluecolor developed and within an hour solumamas tion was practicallycomplete. The reaction mixture was allowed to stand overnight and thenwas cooled for one hour in the refrigerator. The heavy precipitate ofproduct, u-chloropregnane-3B,17dc-diol-20-one, was filtered, washed withmethanol and dried under vacuum; Weight 1.0 gram, melting point 200-205C. Boiling with ethyl acetate dissolved little of the product but raisedthe melting point to 205210 C. The infrared spectrum showed hydroxyl at2.82 and 2.98 carbonyl at 5.90 1 and no acetate grouping. Rotation inpyridine solution [a] +1 C.

Anaylsis.-Calcd. for C H O Cl: C, 68.36; H, 9.02; Cl, 9.61. Found: C,68.33; H, 9.03; Cl, 9.51.

EXAMPLE 7 4-pregnen-1 7a-0l-3,20-dione A chromic anhydride-pyridinecomplex was formed by adding 1.3 grams (13 millimoles) of chromicanhydride in small portions with stirring to 13 milliliters of pyridinewhile keeping the temperature below 25 C. To this stirred slurry wasadded 1.3 grams (3.5 millimoles) of5a-chloropregnane-ilfi-l7a-diol-20-one in 26 milliliters of pyridine. Noheat of reaction was observed but within one-half hour the mixture hadbecome dark brown. After stirring overnight the reaction was poured into500 milliliters of dilute sodium hydroxide solution. The precipitatedproduct 5m-chloro-pregnan-17a-ol-3,20-dione was stirred for one hour,filtered and washed with water.

The product was dissolved in 25 milliliters of pyridine and 50milliliters of methanol, filtered to remove insoluble inorganicmaterial. and treated with l0 milliliters of 2.5 molar sodium hydroxidesolution at room temperature for one hour. The reaction mixture was thendiluted with milliliters of water and refrigerated for one hour.Filtration of the solid precipitate, followed by washing with water anddrying under vacuum yielded 0.6 gram of l7-hydroxyprogesterone, meltingpoint 200 -2l2 C., A maximum 2420 A., E% 488. A sample for analysis wasrecrystallized from ethanol, melting point 2l3-218 C. Identity of thesample with authentic material was established by infrared analysis andmixed melting point.

Analysis.-Calcd. for C H O C, 76.32; H, 9.15. Found: C, 76.77; H, 9.58.

Any departure from the above description which conforms to thepresentinvention is intended to be included in the scope of the claims.

What is claimed is:

1. A process which comprises reacting S-halo-pregnan- 17a-Ol-3,20-di0118with a basic substance selected from the group consisting of hydroxides,carbonates and bicarbonates of alkali metals and alkaline earth metalsto form 4-pregnen-l7u-ol-3,20-dione.

2. The process of claim 1, wherein the basic substance is sodiumhydroxide.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS WHICH COMPRISES REACTING 5-HALO-PREGNAN17$-0L-3,20-DIONEWITH A BASIC SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDROXIDE,CARBONATES AND BICARBONATES OF ALKALI METALS AND ALKALINE EARTH METALSTO FORM 4-PREGNEN-17A-OL-3,20-DIONE.